In magnetic recording, it is necessary to reduce recording bit size in order to increase recording density. However, in order to stably maintain small recording bits on a recording medium, the recording medium must be made using a magnetic material with high magnetic anisotropy (or high magnetic coercive force). In order to perform a write operation with respect to a recording medium with high magnetic anisotropy, recording has to be performed using a write magnetic field of commensurate strength, but it is said that the write magnetic field intensity of write heads will become inadequate in the future. As such, as in microwave assisted magnetic recording, thermally assisted magnetic recording, etc., recording methods are being studied where recording is performed by temporarily reducing the anisotropy field of a medium only when magnetic recording is performed.
In microwave assisted magnetic recording, a recording medium is locally excited by irradiating areas on the order of nanometers with a strong high-frequency magnetic field in the microwave band, and information is recorded by thus reducing the magnetization switching field. Because magnetic resonance is utilized, unless a microwave with a frequency that is proportionate to the anisotropy field of the medium is used, significant magnetization switching field reduction effects cannot be attained.
JP7-244801A discloses a technique for recording information by performing Joule heating or magnetic resonance heating on a magnetic recording medium by means of a high-frequency magnetic field, and thus locally reducing the magnetic coercive force of the medium. In addition, U.S. Pat. No. 7,256,955 discloses a technique for recording information by applying to a recording medium a magnetic field in which a perpendicular magnetic write head drive current is modulated with a high frequency current, inducing a high frequency magnetic field in the magnetic recording medium, and locally placing the recording medium in a state of magnetic resonance, thereby reducing the magnetization switching field. In addition, JP2007-299460A discloses a technique for performing microwave assisted magnetic recording by providing, besides a main coil for main pole excitation and on a magnetic head, a small auxiliary coil for generating microwaves.
On the other hand, in TMR 2007-B6, the paper submission for an oral session at the 2007 TMRC (The Magnetic Recording Conference) international conference, there is disclosed a technique for performing microwave assisted magnetic recording by generating microwaves by disposing, near a magnetic recording medium adjacent to a main pole of a perpendicular magnetic head, a magnetization rotation body that rotates at high speed by way of a spin torque.
Patent Document 1: JP7-244801A
Patent Document 2: U.S. Pat. No. 7,256,955
Patent Document 3: JP2007-299460A
Non-Patent Document 1: TMR 2007-B6